In the Twelve Labors of Hercules, Hephaestus forged the bronze rattle used against the Stymphalian birds.
The birds could not easily be attacked while hidden among the reeds of Lake Stymphalia. Athena therefore gave Hercules a loud bronze device, often translated as a rattle or clapper, which had been made by Hephaestus.
Hephaestus was the Greek god associated with fire, metalworking, smithing, and craftsmanship. His role explains why the object is specifically described as bronze and why it is treated as a special divine tool rather than an ordinary household rattle.
After Hercules used the noise to force the birds into the open, he shot many of them. The story is sometimes simplified to say that Athena merely gave him a rattle, while omitting its maker. The maker is Hephaestus, not Ares, although both gods are associated with aspects of warfare.